Chewelah climate

Chewelah Frost Dates and Growing Season

NOAA 1991-2020 normals for Chewelah, 1.9 km from Chewelah, elevation 1670 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Chewelah. A median date has an even chance of a later freeze in spring, or an earlier one in fall.

The last spring freeze typically comes around May 16 and the first fall freeze around September 15, a growing season of about 120 days.

Median at 32°F
last May 16, first September 15
Median at 28°F
last April 30, first September 28

Last freeze in spring

The chance of a later freeze than the date shown. At 10 percent, one spring in ten still freezes after the date; planting after the 10 percent date for 32°F is the cautious choice.

Threshold10%20%30%40%50%60%70%80%90%
36°F–––––––––
32°FJun 7May 31May 25May 20May 16May 12May 9May 5Apr 30
28°FMay 14May 8May 5May 1Apr 30Apr 27Apr 23Apr 18Apr 12
24°FApr 30Apr 24Apr 18Apr 14Apr 8Apr 3Mar 31Mar 25Mar 17
20°FApr 8Mar 31Mar 27Mar 21Mar 16Mar 13Mar 10Mar 6Mar 1
16°FMar 17Mar 12Mar 9Mar 6Mar 3Feb 28Feb 25Feb 21Feb 12

First freeze in fall

The chance of an earlier freeze than the date shown. At 10 percent, one fall in ten freezes before the date.

Threshold10%20%30%40%50%60%70%80%90%
36°F–––––––––
32°FSep 1Sep 5Sep 8Sep 12Sep 15Sep 18Sep 21Sep 24Sep 29
28°FSep 15Sep 19Sep 22Sep 26Sep 28Oct 1Oct 3Oct 7Oct 13
24°FSep 28Oct 1Oct 3Oct 6Oct 10Oct 13Oct 17Oct 22Oct 28
20°FOct 5Oct 10Oct 16Oct 20Oct 24Oct 29Nov 1Nov 6Nov 17
16°FOct 15Oct 24Oct 30Nov 3Nov 9Nov 14Nov 21Nov 28Dec 7

Growing season length

Days between the last spring and first fall freeze at each threshold, with the chance of a season at least that long.

Threshold10%20%30%40%50%60%70%80%90%
36°F1059891847974675848
32°F14313613012612011410910290
28°F175168162157153148144138131
24°F210202196191186181175168160
20°F248237229224218213207201191
16°F285271263256249244237230220

How often it gets that cold

The share of years with at least one night at or below each temperature.

36°F or colder
100% of years
32°F or colder
100% of years
28°F or colder
100% of years
24°F or colder
100% of years
20°F or colder
100% of years
16°F or colder
100% of years

Degree days

A degree day is one degree of the daily mean temperature beyond a base, for one day. Heating degree days count cold (the fuel a house burns), cooling degree days heat, growing degree days the warmth a crop needs; each crop has its own base.

Heating degree days, base 65°F
7,065
Cooling degree days, base 65°F
261
Growing degree days, base 40°F
3,763
Growing degree days, base 45°F
2,729
Growing degree days, base 50°F
1,864
Growing degree days, base 55°F
1,156
Growing degree days, base 60°F
615

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,19000
February96500
March82302
April555033
May3106187
June15927320
July45121541
August5196510
September23610237
October620034
November92701
December1,18400

What this means

NOAA computes these from the daily lows at the station over 1991-2020, fitting the dates of each year's last and first freeze to a distribution, so a date can be stated at any level of risk. 36°F is a frost risk for tender plants on a clear, calm night, since the ground cools below the air above it; 32°F is a freeze; 28°F is a hard freeze that kills most annuals.

The station is 1.9 km from Chewelah. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00451395 (Chewelah). Public domain.